Gas turbine engines (GTE) produce power by extracting energy from a flow of hot gas produced by combustion of fuel in a stream of compressed air. In general, turbine engines have an upstream air compressor coupled to a downstream turbine with a combustion chamber (“combustor”) in between. Energy is released when a mixture of compressed air and fuel is burned in the combustor. In a typical turbine engine, one or more fuel injectors direct a liquid or gaseous hydrocarbon fuel into the combustor for combustion. The resulting hot gases are directed over blades of the turbine to spin the turbine and produce mechanical power.
Turbine blades and other components of GTEs are subject to creep due to high temperatures and stresses during operation. Components which undergo creep are permanently deformed and can be subject to mechanical failure. Component failure from creep can result from either component breakage due to a reduced cross section of the component as a result of creep deformation, or creep rupture where the rupture creates cracks which may propagate until the component is broken. For turbine blades, creep may cause the entire blade to elongate so that the blade tips contact a stationary structure, for example a turbine casing, and cause unwanted vibrations, blade damage, or loss of performance during operation.
Japanese Patent Application Publication JP10123123A to Konno et al. (the '123 publication) describes a method for estimating creep life of a gas turbine part made from an alloy subject to high temperatures and stresses. According to the '123 publication, in order to estimate the creep life of a gas turbine part, a test operation is carried out, during which an alloy round bar specimen is subjected to various temperatures and stresses. The round bar specimen used during the test is presumed to correspond to a gas turbine part subject to high temperatures and stresses. The test is interrupted at various times, during which an average diameter of a particle of the alloy is measured. Based on at least a change in the average diameter of the particle over a period of time, the creep life of a gas turbine part can be estimated.